IV] THE LARVA OR NYMPH 99 



fig. 43 are perhaps a little shorter than usual for most Dragonflies. 

 The times vary not only with different species, but also according 

 to the strength of the sun's rays, temperature, humidity, and also 

 for both local and individual causes in each separate case. Most 

 Dragonflies emerge at or near dawn. Dragonfly larvae which have 

 been previously disturbed, and have retreated again to the water, 

 generally emerge about midnight, as do also some of the large 

 Aeschninae habitually. Many Dragonflies emerge just before 

 or even during thunderstorms. The most rapid emergence ever 

 witnessed by the author was that of a large number of larvae 

 of Hemigomphus heteroclitus just before a storm. The imagines 

 appeared with great rapidity, crawling straight out of their 

 exuviae. Within ten minutes, many were fully coloured and 

 expanded, and made off quickly into the forest before the storm 

 broke. 



An examination of a cast larval skin shews clearly how the 

 linings of the great tracheal trunks are withdrawn. The dorsal 

 intimae are withdrawn through the mesostigmata, the viscerals 

 through the metastigmata. They are to be seen projecting from 

 the thoracic split in a twisted and shrivelled manner. The ventral 

 intimae are withdrawn through the eighth pair of abdominal 

 spiracles, and can be seen lying tightly stretched along each side of 

 the abdomen, just above the pleurae. From them, branches proceed 

 to each of the other seven pairs of abdominal spiracles. All the 

 spiracles become fully functional at metamorphosis. 



At metamorphosis, as at each ecdysis, the whole of the stomo- 

 daeal and proctodaeal linings are cast off, and shrivel up. The 

 dental folds of the gizzard, which are thicker and more resistant, 

 may often be found within the alimentary canal of the freshly- 

 emerged imago. The gizzard itself becomes reduced in size, and 

 often loses all its teeth. Non-functional remnants of the rectal 

 gills of Anisoptera remain over in the imago. 



72 



